Issue |
A&A
Volume 405, Number 3, July III 2003
|
|
---|---|---|
Page(s) | 999 - 1012 | |
Section | Interstellar and circumstellar matter | |
DOI | https://doi.org/10.1051/0004-6361:20030440 | |
Published online | 30 June 2003 |
Unidentified infrared bands in the interstellar medium across the Galaxy *,**
1
Observatory, University of Helsinki, PO Box 14, 00014 Helsingin yliopisto, Finland
2
Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
Corresponding author: J. Kahanpää, jere.kahanpaa@helsinki.fi
Received:
26
September
2002
Accepted:
18
March
2003
We present a set of 6–12 ISOPHOT-S spectra of the general
interstellar medium of the Milky Way. This part of the spectrum is
dominated by a series of strong, wide emission features commonly called
the Unidentified Infrared Bands. The sampled area covers the inner Milky
Way from l = -60°to +60° with a ten-degree step in
longitude and nominal latitudes b = 0°, ±1°. For each
grid position the actual observed direction was selected from IRAS 100
maps to minimize contamination by point sources and molecular
clouds. All spectra were found to display the same spectral features.
Band ratios are independent of band strength and Galactic coordinates. A
comparison of total observed flux in band features and IRAS 100
emission, a tracer for large interstellar dust grains, shows high
correlation at large as well as small (1´) scales. This implies a
strong connection between large dust grains and the elusive band
carriers; the evolutionary history and heating energy source of these
populations must be strongly linked. The average mid-infrared
spectrum of the Milky Way is found to be GROUP the average
spectrum of spiral galaxy NGC 891 GROUP The common spectrum can therefore
be used as a template for the 6–12
emission of late-type spiral galaxies.
Finally, we show that interstellar extinction only
weakly influences the observed features even at
,
where the silicate absorption feature is strongest.
Key words: ISM: lines and bands / ISM: dust, extinction / infrared: ISM / Galaxy: disk / galaxies: ISM
© ESO, 2003
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